Italian Territory at Risk of Floods

Flood 19 September 2023 Emilia Romagna

decreto legislativo n49.pdf

Legislative Decree n.49 of 23 February 2010

What is a flood?

Flooding is a phenomenon that occurs when water exceeds the boundaries of rivers, lakes or other bodies of water, whether natural or artificial, inundating areas that are not normally covered with water. This process, called overflow or inundation, is part of the natural cycle of a watercourse, but the term flood is often used to indicate a meteorological event that causes significant damage, especially when it affects urbanized or agricultural areas.

Floods can occur in different ways: through the flooding of a river, the accumulation of water in low-lying areas or the invasion of sea water in coastal areas. They are closely linked to extreme meteorological phenomena, such as intense and prolonged rainfall, rapid melting of snow, storms or cyclones. Furthermore, the phenomenon can be amplified by factors such as the reduced drainage capacity of the soil or poor land management. [1]

From a regulatory point of view, in Italy, flooding is governed by Legislative Decree no. 49 of 23 February 2010 (I leave you the PDF here on the left), which defines the event as a temporary flooding of areas not normally submerged. The definition includes the transport and mobilization of high-density sediments and covers flooding caused by rivers, streams, lakes and artificial drainage networks, as well as storm surges affecting coasts. However, floods caused by sewage systems are not considered floods. Floods are classified as phenomena of hydrogeological instability, together with landslides and mudslides, and represent a serious risk for the safety of people and infrastructures, especially in highly urbanized or sensitive areas from a geomorphological point of view. Flood risk prevention and management are therefore crucial for mitigating damage and protecting the environment.

CHARACTERISTICS OF A FLOOD [1]

Floods have highly variable characteristics that depend on different factors and local conditions, thus influencing their degree of danger and impact. Some floods may occur suddenly, others more gradually; they can affect limited areas or extend over vast regions, involving coastal or inland areas. Their consequences can vary significantly in severity. The main types of flooding include:

River Flood: when a river or watercourse overflows beyond its banks, submerging adjacent areas.
Coastal Flood: occurs when coastal areas are inundated by rising sea levels or intense storm surges.
Storm wave (Storm Surge): caused by storms or cyclones, it is a sudden rise in sea level that inundates the coasts.
Inland Flood: More commonly called a flood, it occurs in inland areas far from rivers or seas, often due to heavy rainfall.
Flash Flood: A rapid flooding of areas following torrential rain or sudden failures of levees and dams.

MAIN CAUSES [1]

Heavy rainfall: Rain is the most common cause of flooding, both in the case of weak and prolonged rainfall and very intense rainfall concentrated in a short time. If the soil or drainage systems cannot absorb or drain the water in time, the accumulation causes flooding.
Natural floods: Rivers, due to morphological changes, can modify their natural course. Accumulations of sediment, variations in the riverbed or natural obstacles such as vegetation can alter the flow of water, causing flooding.
Human interventions: Hydraulic works such as dams, embankments or diversion channels can represent a risk if poorly designed or managed. Levee breaks, overflows or malfunctions of dams can cause devastating floods, while hydraulic works upstream can have negative impacts downstream, altering natural flow.
Storm surges, tsunamis and tsunamis: Extreme marine events, such as rogue waves or tsunamis, can cause sea levels to rise, inundating coastal areas.
Melting snow and glaciers: When large amounts of snow or ice melt rapidly, often in the spring or due to climate change, they flow into waterways, creating a surplus of water that is difficult to manage.

EFFECTS [1]

Main risks generated by floods

Damage to buildings and infrastructure: Water can penetrate homes, public buildings and industrial facilities, causing significant damage. The flooding of basements, warehouses or habitable spaces can lead to the loss of goods and the interruption of economic activities. Water can also compromise the structural stability of buildings, increasing repair and recovery costs.
Damage to roads and bridges: Road infrastructure is particularly vulnerable. Roads, bridges and railways can be damaged or destroyed by the force of the water, interrupting communication lines and making rescue and evacuation operations difficult. Erosion caused by water runoff can gouge deep cavities or fractures in the pavement, causing additional safety problems.
Disruption of communications networks: Floods can affect electricity, telephone and internet networks, isolating affected areas. Malfunctioning communications infrastructure can hamper rescue efforts and worsen the situation for those stranded in flooded areas.
Loss of life: Fast-moving floods, such as flash floods, can overwhelm people, causing their deaths. The water can reach levels and speeds sufficient to carry away people, vehicles and large objects, representing a serious risk for those who cannot reach safety in time.
Economic impact: Economic activities in the affected areas suffer severe disruptions. Damage to businesses and lost production can have long-term impacts on the local community, in addition to the costs associated with rebuilding and rehabilitating infrastructure.
Environmental contamination: Floods can carry with them waste, chemicals and toxic materials, contaminating surrounding water and land. This can cause serious health problems, especially if drinking water becomes contaminated.

rapporto_dissesto_idrogeologico_italia_ispra_356_2021_finale_web.pdf

FLOOD IN EMILIA ROMAGNA [2]

The Italian territory is extremely vulnerable to the risk of flooding, as emerges in detail in the report on hydrogeological instability published by ISPRA (Higher Institute for Environmental Protection and Research). The report provides an updated reference framework on the danger of landslides and floods across the entire national territory and presents the risk indicators relating to the population, families, buildings, businesses and cultural heritage. (I leave you the PDF here on the left)

The ISPRA 2021 report identifies Emilia-Romagna as the Italian region with the highest percentage of territory subject to flood risk. 100% of the Emilia-Romagna territory is subject to high, medium or low risk of floods (in Italy it is around 30%). In this Region all three risk scenarios are well above the national average. As also confirmed by the ISPRA IroGeo portal on hydrogeological risk in Italy, among the 6.8 million people who live in areas at medium risk of floods in our country, 40% (2.7 million people) reside in Emilia alone -Romagna. The floods affecting Emilia-Romagna can be explained by a combination of natural and anthropogenic factors that make this region vulnerable.

Geography and nature of the floodplain

The entire Po Valley, of which Emilia-Romagna is part, is an alluvial plain. This means that it was formed by sedimentation brought by rivers, in particular the Po and its tributaries. Sediment deposited over thousands of years has created an area that is flat and naturally prone to flooding. Flood events, therefore, are part of the natural cycle of this area, although human land management has exacerbated the problem.

Geographical conformation of the area

The specific area in Emilia-Romagna is located in a sort of "basin", delimited to the north by the Po, to the south by the Apennine mountains and to the east by the Romagna coast. This creates a real "floodable triangle" where the water tends to flow together and stagnate in the event of heavy rain. Furthermore, the presence of numerous smaller watercourses makes the risk of flooding even more likely, as these tributaries can easily overflow in the event of exceptional rainfall.

High population density and urbanization

A further factor is the high population density of Emilia-Romagna, a region with around 4.5 million inhabitants. The population is evenly distributed across much of the territory, increasing the risk of floods damaging homes, infrastructure and economic activities. Overbuilding and land consumption further aggravate the situation. According to the SNPA (National System for Environmental Protection), between 10% and 30% of the land in this area is urbanized, which severely limits the soil's ability to absorb rainwater. This contributes to increasing the risk of flooding in the event of heavy rain.

This combination of natural and urban factors makes Emilia-Romagna one of the areas most at risk of flooding in Italy and Europe, with serious consequences for safety and the local economy.

ISPRA, Eco Atlas, Geology and fragility of the territory.

Bibliography

[1] NOAA National Severe Storms Laboratory: https://www.nssl.noaa.gov/, https://www.nssl.noaa.gov/education/svrwx101/floods/

[2] ISPRA: https://www.isprambiente.gov.it/it/banche-dati/banche-dati-folder/suolo-e-territorio https://sinacloud.isprambiente.it/portal/apps/storymaps/stories/68fd822ebec94fc28ebe9c2f7ea410a9

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